Nitrate Contamination in Groundwater on an Urbanized Dairy Farm

• Published in: Environmental science & technology Vol. 42; no. 13; pp. 4683 - 4688
• Main Authors: Showers, William J, Genna, Bernard, McDade, Timothy, Bolich, Rick, Fountain, John C
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.07.2008
• Subjects: Applied sciences; Bromides - analysis; Characterization of Natural and Affected Environments; Chlorides - analysis; Contamination; Dairy farms; Dairying; Drinking water; Environmental Monitoring - statistics & numerical data; Exact sciences and technology; Flow Injection Analysis; Groundwater; Magnetics; Nitrate content; Nitrates; Nitrates - analysis; Nitrogen Isotopes - analysis; North Carolina; Pollution; Urban areas; Urban Renewal; Urbanization; Water Pollutants, Chemical - analysis; Water Supply - analysis; North Carolina; United States; Europe; Piedmont Province; America; Italy; North America; United States > US; Piedmont North Carolina; USA, North Carolina; USA, North Carolina, Piedmont; Isotopic analysis; Drinking water; Organic matter; Water supply; Carbon dioxide; Identification; Nitrates; Urban area; Biological purification; Water well; Health and environment; Chlorides; Rural area; Oxidation; Public health; Ground water; Aerobe; Housing; Coastal lagoon; Pasture; Trend analysis; Denitrification; Lagooning; Suburban zone; Water pollution; Regulation; Waste water purification; Animal waste
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es071551t

Urbanization of rural farmland is a pervasive trend around the globe, and maintaining and protecting adequate water supplies in suburban areas is a growing problem. Identification of the sources of groundwater contamination in urbanized areas is problematic, but will become important in areas of rapid population growth and development. The isotopic composition of NO3 (δ15NNO3 and δ18O NO3), NH4 (δ15NNH4), groundwater (δ2Hwt and δ18Owt) and chloride/bromide ratios were used to determine the source of nitrate contamination in drinking water wells in a housing development that was built on the site of a dairy farm in the North Carolina Piedmont, U.S. The δ15NNO3 and δ18O NO3 compositions imply that elevated nitrate levels at this site in drinking well water are the result of waste contamination, and that denitrification has not significantly attenuated the groundwater nitrate concentrations. δ15NNO3 and δ18ONO3 compositions in groundwater could not differentiate between septic effluent and animal waste contamination. Chloride/bromide ratios in the most contaminated drinking water wells were similar to ratios found in animal waste application fields, and were higher than Cl/Br ratios observed in septic drain fields in the area. δ18Owt was depleted near the site of a buried waste lagoon without an accompanying shift in δ2Hwt suggesting water oxygen exchange with CO2. This water−CO2 exchange resulted from the reduction of buried lagoon organic matter, and oxidation of the released gases in aerobic soils. δ18Owt is not depleted in the contaminated drinking water wells, indicating that the buried dairy lagoon is not a source of waste contamination. The isotope and Cl/Br ratios indicate that nitrate contamination in these drinking wells are not from septic systems, but are the result of animal waste leached from pastures into groundwater during 35 years of dairy operations which did not violate any existing regulations. Statutes need to be enacted to protect the health of the homeowners that require well water to be tested prior to the sale of homes built on urbanized farmland.